1. Field
One embodiment of the present invention relates to a method of manufacturing a discrete track recording medium and a discrete track recording medium manufactured by this method.
2. Description of the Related Art
Recently, in the magnetic recording medium incorporated into hard disk drives (HDDs), there is an increasing problem of disturbance of enhancement of track density due to interference between adjacent tracks. In particular, a serious technical subject is reduction of write blurring due to fringe effect of magnetic fields from a write head.
To solve such a problem, for example, a discrete track recording-type patterned medium (DTR medium) has been proposed in which recording tracks are physically separated. The DTR medium is capable of reducing a side erase phenomenon of erasing information of an adjacent track in writing or a side read phenomenon of reading out information of an adjacent track in reading, and is hence known to enhance the track density. Therefore, the DTR medium is expected as a magnetic recording medium capable of providing a high recording density.
To read and write a DTR medium with a flying head, it is desired to flatten the surface of the DTR medium. Specifically, in order to separate adjacent tracks completely, for example, a protective layer with a thickness of about 4 nm and a magnetic recording layer with a thickness of about 20 nm are removed to form recesses of about 24 nm in depth, thereby forming magnetic patterns. On the other hand, since the designed flying height of the flying head is about 10 nm, head flying is made unstable if deep recesses are left remained. Accordingly, it has been attempted to fill the recesses between magnetic patterns with a nonmagnetic material so as to flatten the medium surface for ensuring flying stability of the head.
Conventionally, the following method has been proposed to obtain a DTR medium having a flat surface by filling the recesses between magnetic patterns with a nonmagnetic material. For example, in a known method, by two-stage bias sputtering, the recesses between magnetic patterns are filled with a nonmagnetic material, and a DTR medium of a flat surface is manufactured (see Japanese Patent No. 3686067). However, when the recesses of the DTR medium are filled with a nonmagnetic material by bias sputtering, it has been known that the magnetic recording medium is deteriorated and degenerated due to temperature rise by substrate bias.
The temperature rise may be avoided by performing bias sputtering while forcedly cooling the substrate, but to forcedly cool the substrate, the rear surface of the substrate must be fitted tightly to the cooling mechanism. In this case, the rear surface of the substrate may be injured, and it has been found that the both surfaces cannot be processed by bias sputtering in principle. If the both surfaces cannot be processed, the recording capacity of the DTR medium is reduced to half.
Hence, by employing a deposition method capable of processing both surfaces, and in order to flatten the surfaces of the DTR medium, it may be considered to repeat the processes of depositing a nonmagnetic material in the recesses between the magnetic patterns and on the magnetic patterns and etching back the nonmagnetic material. However, when deposition and etching-back of nonmagnetic material are repeated, the thickness of the nonmagnetic material may be uneven, and favorable reproduction may be difficult. Since such thickness dispersion of nonmagnetic material varies depending on manufacturing apparatuses, the problem cannot be solved substantially by a method of adjusting the manufacturing apparatuses individually.